Control device for vehicle and control method for vehicle

ABSTRACT

A control device for a vehicle includes a drive shaft, an engine coupled to the drive shaft, an electric motor coupled to the drive shaft, and a control unit. The control unit increases a torque of the electric motor when an accelerator pedal opening increases to equal to or more than a predetermined degree of opening during switching of driving sources, and decreases the torque of the electric motor while increasing the torque of the engine after a change of the torque of the engine turns to increase.

TECHNICAL FIELD

The present invention relates to a control device and a control methodfor a vehicle including an engine and an electric motor as drivingsources.

BACKGROUND ART

JP2008-273460A discloses that, in a vehicle including an engine and amotor-generator as driving sources, the driving sources are switched byexecuting a control that gradually increases a torque of themotor-generator while gradually decreasing a torque of the engine whentransitioning from a traveling mode (HEV mode) in which traveling isperformed by both the engine and the motor-generator to a traveling mode(EV mode) in which traveling is performed by only the motor-generator.

SUMMARY OF INVENTION

According to a control disclosed in JP2008-273460A, a generation of ashock in association with switching of the driving sources can besuppressed when the traveling mode is transitioned from the HEV mode tothe EV mode. However, in the above-described document, no measure ismentioned for the case where an accelerator pedal is pressed during theswitching of the driving sources, in other words, while the torque ofthe engine is being decreased, and a return to the HEV mode isnecessary.

An object of the present invention is to secure a driving response of avehicle when an accelerator pedal is pressed during switching of drivingsources.

According to an aspect of the present invention, a control device for avehicle includes a drive shaft, an engine coupled to the drive shaft andan electric motor coupled to the drive shaft. The control device for thevehicle includes a control unit that increases a torque of the electricmotor when an accelerator pedal opening increases to equal to or morethan a predetermined degree of opening during switching of drivingsources in which the torque of the electric motor is increased while atorque of the engine is decreased, and decreases the torque of theelectric motor while increasing the torque of the engine after a changeof the torque of the engine turns to increase.

According to another aspect of the present invention, a control methodfor a vehicle is provided. The vehicle includes a drive shaft, an enginecoupled to the drive shaft and an electric motor coupled to the driveshaft. The control method for the vehicle includes increasing a torqueof the electric motor when an accelerator pedal opening increases toequal to or more than a predetermined degree of opening during switchingof driving sources in which the torque of the electric motor isincreased while a torque of the engine is decreased, and decreasing thetorque of the electric motor while increasing the torque of the engineafter a change of the torque of the engine turns to increase.

The above-described configuration ensures securing a driving response ofa vehicle while suppressing a generation of a shock when an acceleratorpedal is pressed due to, for example, a change-of-mind of a driverduring switching of driving sources.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram illustrating an overall configuration of avehicle drive system according to one embodiment of the presentinvention.

FIG. 2 is a flowchart illustrating a basic procedure of a driving sourceswitching control (switching from engine traveling to EV traveling)according to the embodiment.

FIG. 3 is a flowchart illustrating a content of a process relating toreturning to the engine traveling of the driving source switchingcontrol.

FIG. 4 is an explanatory diagram illustrating a trend of an operatingrange map according to the one embodiment of the present invention.

FIG. 5 is an explanatory diagram illustrating an operation of thevehicle drive system by the driving source switching control accordingto the embodiment.

FIG. 6 is an explanatory diagram illustrating an operation of a vehicledrive system according to a comparative example.

FIG. 7 is an explanatory diagram illustrating an operation of thevehicle drive system when transitioned to an accelerator off state.

DESCRIPTION OF EMBODIMENTS

The following describes embodiments of the present invention withreference to the drawings.

(Configuration of Vehicle Drive System)

FIG. 1 schematically illustrates an overall configuration of a vehicledrive system P according to one embodiment of the present invention.

The vehicle drive system P includes an engine 1 and a motor-generator 5as driving sources. The engine 1 and the motor-generator 5 are bothcoupled to right and left driving wheels 8. On a power transmission pathcoupling the engine 1 to the driving wheels 8, an automatic transmissionTM is interposed. The motor-generator 5 is coupled to the driving wheels8 via the automatic transmission TM (specifically, a variator 4). Whilein the embodiment, the engine 1 and the motor-generator 5 are coupled inparallel to the variator 4 via independent power transmission paths, theengine 1 and the motor-generator 5 may be disposed on an identical powertransmission path that extends from the variator 4.

The automatic transmission TM is a continuously variable transmission,and includes a torque converter 2, a clutch 3, and the variator 4 in anorder from a side close to the engine 1 on the power transmission pathapproaching the driving wheels 8. The automatic transmission TM convertsa rotative power input from the engine 1 and the motor-generator 5 at apredetermined speed ratio, and outputs to the driving wheels 8 via adifferential gear 6.

The torque converter 2 includes a pump impeller 21 coupled to an inputshaft of the torque converter 2 and a turbine runner 22 coupled to anoutput shaft of the torque converter 2, and transmits the input rotativepower to the output shaft via a fluid dynamic action. The torqueconverter 2 further includes a lock-up clutch 23 coupled to the outputshaft, and directly couples the input shaft to the output shaft of thetorque converter 2 by bringing the lock-up clutch 23 into an engagedstate to ensure reducing a transmission loss due to a fluid connection.An engagement and a disengagement of the lock-up clutch 23 can beswitched by controlling a hydraulic pressure affecting the lock-upclutch 23.

The clutch 3 is disposed between the torque converter 2 and the variator4, and includes a friction engaging element (hereinafter referred to asan “input element”) 31 coupled to a crankshaft (an output shaft of thetorque converter 2 in this embodiment) of the engine 1 and a frictionengaging element (hereinafter referred to as an “output element”) 32coupled to the input shaft (specifically, a rotation shaft of a primarypulley 41) of the variator 4. The clutch 3 engages and disengages theinput element 31 and the output element 32 to couple and cuts off theengine 1 to/from the variator 4 and the driving wheels 8. The operationof the clutch 3 is controlled by adjusting the hydraulic pressureaffecting the input element 31 or the output element 32.

The variator 4 includes the primary pulley 41 and a secondary pulley 42as variating elements, and includes a metal belt 43 wound between thispair of pulleys 41 and 42. The variator 4 ensures steplessly changing aspeed ratio by changing a ratio of a contact diameter of the metal belt43 on the primary pulley 41 and the secondary pulley 42. The speed ratioof the variator 4 is controlled by adjusting the hydraulic pressureaffecting movable sheaves of the primary pulley 41 and the secondarypulley 42, and changing widths of V-grooves formed between the movablesheaves and fixed sheaves.

The motor-generator 5 can function as an electric generator not onlyfunctioning as an electric motor. It is possible to employ an electricmotor operable only as the electric motor, instead of themotor-generator 5. The motor-generator 5 includes a rotor 51 coupled tothe output shaft and a stator 52 disposed in a concentric manner withthe rotor 51 in the peripheral area of the rotor 51. By controlling asupply of the electric power to an electromagnetic coil disposed in thestator 52, the motor-generator 5 can function as the electric motor togenerate a torque. The torque of the motor-generator 5 is transmitted toa rotation shaft of the variator 4 (an input shaft and the rotationshaft of the primary pulley 41 in this embodiment) via a powertransmission medium, such as a gear. The supply of the electric power tothe motor-generator 5 is controlled by a power control unit in which aninverter 55 is incorporated. A direct current supplied from a battery 9is converted into a three-phase alternating current by the inverter 55,and is supplied to the motor-generator 5. Meanwhile, the alternatingcurrent generated by a regeneration operation of the motor-generator 5is converted into a direct current by the inverter 55, and is suppliedto the battery 9. The battery 9 is rechargeable by the current suppliedfrom the motor-generator 5.

A rotative power after shifting that is output from the automatictransmission TM is transmitted to a drive shaft 7 via a gear train setto a predetermined gear ratio and the differential gear 6 to rotate thedriving wheels 8. Thus, in the embodiment, while the engine 1 is coupledto the drive shaft 7 by the clutch 3 in a disengageable/engageablemanner, the motor-generator 5 is coupled to the drive shaft 7 withoutvia the clutch 3. Not only limited to the engine 1 and the drive shaft7, but it is obvious that the motor-generator 5 may be coupled to thedrive shaft 7 by interposing a clutch in a disengageable/engageablemanner between the motor-generator 5 and the drive shaft 7.

The embodiment includes the lock-up clutch 23 of the torque converter 2,the input element 31 and the output element 32 of the clutch 3, and amechanical drive type oil pump 10 as a source of generation of thehydraulic pressure affecting the variating elements 41 and 42 of thevariator 4. The oil pump 10 is driven by a rotative power of the engine1, increases the hydraulic oil pressure, and supplies the hydraulic oilto each portion via a hydraulic pressure control circuit 11. FIG. 1illustrates hydraulic pressure supply passages from the hydraulicpressure control circuit 11 to each portion by dotted lines with arrowheads.

The embodiment includes an electrically operated type oil pump 12 inaddition to the oil pump 10. The oil pump 12 is actuated by an electricpower supplied from the battery 9, and increases the hydraulic oilpressure. The hydraulic oil after being increased can be supplied toeach portion via the hydraulic pressure control circuit 11 similarly tothe case by the oil pump 10. The electrically operated type oil pump 12can, for example, control the hydraulic pressure applied to the clutch 3during a stop of the engine 1.

(Configuration and Basic Operation of Control System)

Operations of the engine 1 and the motor-generator 5 are controlled by acontroller 101. It is also possible to configure as a combination of anengine controller and a motor-generator controller by distributingfunctions possessed by the controller 101 relating to the control of theengine 1 and the motor-generator 5 to a plurality of controllers. Thecontroller 101 is configured as an electronic control unit, and isformed of a central processing unit (CPU), various kinds of storagedevices, such as a RAM and a ROM, and a microcomputer including, forexample, input/output interfaces.

The controller 101 is one that provides a function of a “control unit”according to the embodiment, and a “control device for a vehicle”according to the embodiment is configured by including the drive shaft7, the engine 1, and the motor-generator 5 besides the controller 101.While in the embodiment, the rotation shaft (hereinafter, referred to asan “output shaft” in some cases) 7 coupled to the driving wheels 8 issupposed to be a “drive shaft,” the “drive shaft” is not limited to theoutput shaft 7, and may be any shaft that can transmit the rotativepower from the engine 1 and the motor-generator 5 to the driving wheels8, such as a rotation shaft of the primary pulley 41 or a rotation shaftof the secondary pulley 42. In this sense, the “control device for avehicle” can be configured by including the rotation shaft of theprimary pulley 41 or the like instead of the output shaft 7.

In the embodiment, a signal from an accelerator sensor 111 that detectsan operation amount (hereinafter, referred to as an “accelerator pedalopening”) APO of the accelerator pedal by a driver, and a signal from avehicle speed sensor 112 that detects a vehicle traveling speed(hereinafter, referred to as a “vehicle speed”) VSP are input to thecontroller 101 in relation to a driving force control of the vehicle, aswell as signals from various kinds of sensors that detect, for example,a rotation speed NE of the engine 1, a temperature TW of a cooling waterof the engine 1, a rotation speed Npri of the primary pulley 41, arotation speed Nsec of the secondary pulley 42, a pressure Ppri of thehydraulic oil affecting the primary pulley 41, a pressure Psec of thehydraulic oil affecting the secondary pulley 42, a temperature Toil ofthe hydraulic oil of the automatic transmission TM, and a position SFTof a shift lever, are input. In the embodiment, the vehicle speed sensor112 is disposed to be able to measure a rotation speed of the driveshaft 7, and the controller 101 calculates the vehicle speed VSP on thebasis of a signal from the vehicle speed sensor 112.

The controller 101 determines a region to which a current operatingstate of the vehicle belongs on the basis of the various kinds ofsignals, such as the accelerator pedal opening APO and the vehicle speedVSP, and switches the driving sources between the engine 1 and themotor-generator 5 corresponding to its determination result.Specifically, while the motor-generator 5 serves as the driving sourcein an operating range (hereinafter, referred to as a “first region”) R1on a low load side with the accelerator pedal opening APO being lessthan a predetermined degree of opening APO1, the engine 1 serves as thedriving source in an operating range (hereinafter, referred to as a“second region”) R2 on a high load side with the accelerator pedalopening APO being equal to or more than the predetermined degree ofopening APO1. Thus, in the embodiment, the driving source isalternatively selected between the engine 1 and the motor-generator 5.However, while only the motor-generator 5 serves as the driving sourcein the first region R1, the engine 1 and the motor-generator 5 may beused in combination as the driving source in the second region R2 toexecute a torque assist by the motor-generator 5.

FIG. 4 illustrates an exemplary operating range map. The operating rangemap is defined by the accelerator pedal opening APO and the vehiclespeed VSP, and, on the basis of the degree of opening APO1 preliminarilydetermined corresponding to the vehicle speed VSP, the region less thanthe predetermined degree of opening APO1 (illustrated with diagonallines) corresponds to the first region R1 and the region equal to ormore than the predetermined degree of opening APO1 corresponds to thesecond region R2. While in the embodiment, the predetermined degree ofopening APO1 is set to a different value depending on the vehicle speedVSP, specifically, set to a small value as the vehicle speed VSP is in ahigh region, it is also possible to set the predetermined degree ofopening APO1 to a constant value. The controller 101 compares thecurrent accelerator pedal opening APO with the predetermined degree ofopening APO1 on the basis of the vehicle speed VSP to determine theregions R1 and R2 to which the operating states belong.

When the accelerator pedal opening APO is less than the predetermineddegree of opening APO1, and the motor-generator 5 is selected as thedriving source, the engine 1 is stopped and the clutch 3 is disengaged.The traveling in such a state is referred to as an “EV traveling.”Meanwhile, when the accelerator pedal opening APO is equal to or morethan the predetermined degree of opening APO1, and the engine 1 isselected as the driving source, the supply of the electric power to themotor-generator 5 is stopped and the clutch 3 is engaged to ensure thetransmission of the rotative power to the drive shaft 7 from the engine1. The traveling in such a state is referred to as an “enginetraveling.”

When the accelerator pedal is returned from the state where theaccelerator pedal opening APO is equal to or more than the predetermineddegree of opening APO1, and the operating state is transitioned from thesecond region R2 to the first region R1, to switch the driving sourcefrom the engine 1 to the motor-generator 5, in other words, whenswitching from the engine traveling to the EV traveling, the controller101 executes a control to, while gradually decreasing the torque of theengine 1, gradually increase the torque of the motor-generator 5corresponding to the decrease of the engine torque. This suppresses thegeneration of the shock in association with the switching of the drivingsources. The switching of the driving sources from the engine 1 to themotor-generator 5 also occurs, not limited to when the accelerator pedalopening APO is decreased due to returning of the accelerator pedal bythe driver so as to cross over a switching line (=APO1) to a side of thefirst region R1, but even when a travelling resistance is increased andthe vehicle speed VSP is decreased, such as when the vehicle approachesan uphill road from a flat road, without no change in the position ofthe accelerator pedal itself. FIG. 4 indicates an exemplary case of theswitching caused by the driver returning the accelerator pedal by arrowsa1 and a2, and an exemplary case of the switching caused by the increaseof the travelling resistance by an arrow a3.

Here, the case where, during the switching of the driving sources, theaccelerator pedal is pressed, and the accelerator pedal opening APO isincreased to equal to or more than the predetermined degree of openingAPO1 again is assumed. Such a situation corresponds to, for example,when the driver who once returns the accelerator pedal with theintention to decelerate has a change-of-mind to reaccelerate, or when,after the vehicle approaches the uphill road, the driver who feels theinsufficient vehicle speed presses the accelerator pedal with theintention to accelerate.

In this case, the driving source is returned to the engine 1 in order toswitch from the EV traveling to the engine traveling again, and a fuelinjection quantity to the engine 1 is increased in order to ensureoutputting the engine torque corresponding to the accelerator pedalopening APO after the increase. However, there exists a delay in thetorque of the engine 1 until it actually starts to be increased since atorque increase instruction to the engine 1, in other words, since anincrease instruction of the fuel injection quantity. Therefore, onlysimply outputting the torque increase instruction to the engine 1 inresponse to the increase of the accelerator pedal opening APO causes ashortage in the torque transmitted to the drive shaft 7 (hereinafter,referred to as a “drive shaft torque”).

Therefore, in the embodiment, in response to the increase of theaccelerator pedal opening APO during the switching of the drivingsources from the engine 1 to the motor-generator 5, a control toincrease the torque of the motor-generator 5 is executed in conjunctionwith the torque increase instruction to the engine 1. This compensatesthe delay in the engine torque with the torque of the motor-generator 5to secure a driving response of the vehicle. The control executed by thecontroller 101 regarding the switching of the driving sources will bedescribed with reference to the following flowchart.

(Content of Driving Source Switching Control)

FIG. 2 illustrates a basic procedure of the driving source switchingcontrol with a flowchart.

At S101, the signals indicative of the operating state of the vehicle,such as the accelerator pedal opening APO and the vehicle speed VSP, areread.

At S102, it is determined whether the condition is satisfied for thetransition from the engine traveling to the EV traveling or not.Specifically, it is determined whether the operating state hastransitioned from the second region R2 where the accelerator pedalopening APO is equal to or more than the predetermined degree of openingAPO1 to the first region R1 where the accelerator pedal opening APO isless than the predetermined degree of opening APO1 or not. When theoperating state is transitioned to the first region R1, and thecondition is satisfied for the transition from the engine traveling tothe EV traveling, the process proceeds to S103, and when it is not insuch a condition, the process returns to S101 to repeatedly execute theprocess at S101 and 102.

At S103, the switching of the driving sources is started. In theembodiment, the control to increase the torque of the motor-generator 5while decreasing the torque of the engine 1 is executed, and, forexample, while gradually decreasing the torque of the engine 1, thetorque of the motor-generator 5 is increased corresponding to thedecrease of the engine torque. The decrease of the engine torque is, forexample, caused by changing the fuel injection quantity of the engine 1at a decrease rate that ensures the suppressed shock in association withthe switching. The torque of the motor-generator 5 is increased so as tocompensate for the shortage amount of the engine torque with respect tothe drive shaft torque corresponding to the accelerator pedal openingAPO.

At S104, it is determined whether the switching of the driving sourcesfrom the engine 1 to the motor-generator 5 is completed or not. Forexample, it is determined whether the fuel injection quantity of theengine 1 is decreased down to a preliminarily set fuel cut injectionquantity or zero or not. When the fuel injection quantity issufficiently decreased, and the switching of the driving sources iscompleted, the process proceeds to S105, and when it is not yetcompleted, in other words, when the fuel injection quantity is notdecreased down to the fuel cut injection quantity or zero, and it isduring the switching of the driving sources, the process proceeds toS107.

At S105, the clutch 3 is disengaged to cut off the transmission of therotative power to the drive shaft 7 from the engine 1. That is, in theembodiment, after the accelerator pedal opening APO is decreased to lessthan the predetermined degree of opening APO1, and the operating stateis transitioned to the first region R1, the clutch 3 is not disengaged,and the engaged state is maintained until the switching of the drivingsources to the motor-generator 5 is completed.

At S106, the supply of the fuel to the engine 1 is stopped to stop theengine 1.

At S107, it is determined whether the accelerator pedal opening APO isincreased to equal to or more than the predetermined degree of openingAPO1 or not, in other words, after the operating state is transitionedfrom the second region R2 on the high load side to the first region R1on the low load side, whether the operating state is transitioned to thesecond region R2 again or not. When the accelerator pedal opening APO isincreased to equal to or more than the predetermined degree of openingAPO1, the process proceeds to S201 illustrated in FIG. 3, and when theaccelerator pedal opening APO is not increased to equal to or more thanthe predetermined degree of opening APO1, that is, when the acceleratorpedal opening APO still remains in less than the predetermined degree ofopening APO1, the process proceeds to S108.

At S108, the switching of the driving sources is continued, and thetorque of the motor-generator 5 is increased while decreasing the torqueof the engine 1.

At S201, the torque increase instruction is output to the engine 1 inorder to switch the driving sources to the engine 1 again. Specifically,a target value of the engine torque that ensures achieving the driveshaft torque corresponding to the accelerator pedal opening APO afterthe increase is set, and the fuel injection quantity of the engine 1 isincreased on the basis of this target engine torque.

At S202, the torque of the motor-generator 5 is controlled to increasethe torque of the motor-generator 5 so as to compensate for the shortageamount of the actual engine torque with respect to the target driveshaft torque. In the embodiment, this increases an inclination of thetorque change generated by the motor-generator 5 more than that beforethe transition of the operating range, in other words, before theaccelerator pedal opening APO is increased to equal to or more than thepredetermined degree of opening APO1. While the actual engine torque maybe detected by installing a sensor at an appropriate rotating shaft,such as the input shaft of the torque converter 2, it is also possibleto detect by an estimation calculation based on the current enginetorque and the target engine torque by approximating the delay of theactual engine torque with respect to the target engine torque as aprimary delay.

At S203, it is determined whether the change of the torque of the engine1 is shifted to an increase or not. Whether the torque of the engine 1has reached a predetermined value or not after being shifted to theincrease may be determined, not only the change of the engine torquebeing shifted to the increase. This ensures obtaining an effect tocompensate the shortage amount caused by the delay of the engine torquewith the torque of the motor-generator 5 with more certainty.

At S204, decreasing the torque of the motor-generator 5 so as to be incoordination with the increase of the engine torque achieves the driveshaft torque corresponding to the accelerator pedal opening APO, inother words, the drive shaft torque desired by the driver.

At S205, matching of the torque of the engine 1 and the drive shafttorque completes the switching of the driving sources to the engine 1.This completes the transition to the engine traveling, and the vehicletravels using the engine 1 as the driving source. Thus, in theembodiment, the accelerator pedal opening APO is increased to equal toor more than the predetermined degree of opening APO1 during theswitching of the driving sources, and when the driving source isreturned to the engine 1, the clutch 3 is maintained in the engagedstate through the whole control from the start of the driving sourceswitching control (S103) to the completion of the return to the engine 1(S205).

In the embodiment, the functions of the “control unit” are achieved bythe processes at S102 to 104, S107, and S108 in the flowchartillustrated in FIG. 2, and the processes at S201 to 204 in the flowchartillustrated in FIG. 3.

(Description of Operation by Timing Chart)

FIG. 5 schematically illustrates an operation of a vehicle drive systemP by the driving source switching control according to the embodiment bya timing chart, and FIG. 6 illustrates the operation by the comparativeexample. In both FIGS. 5 and 6, a rotational speed NE and a torque TE ofthe engine 1 are indicated by dotted lines, and a rotational speed NMand a torque TM of the motor-generator 5 are indicated by solid lines.Furthermore, a torque (input shaft torque) TSi applied to the inputshaft of the variator 4 is indicated by a two-dot chain line.

For ease of understanding the case of the embodiment (FIG. 5), first,the case of the comparative example (FIG. 6) will be described, andnext, the operation by the control according to the embodiment will bedescribed.

In FIG. 6, the control to switch the driving sources from the engine 1to the motor-generator 5 is executed in order to transition from theengine traveling to the EV traveling when the accelerator pedal isreturned from a state where the operating state is in a medium loadregion (APO APO1) to be transitioned to the low load region (the firstregion R1) where the accelerator pedal opening APO is less than thepredetermined degree of opening APO1 (time t1). The controller 101outputs an instruction to decrease the fuel injection quantity to theengine 1. In conjunction with this, the controller 101 increases thetorque of the motor-generator 5 corresponding to the decrease of theengine torque (time t2) to suppress the generation of the shock inassociation with the switching of the driving sources. When the fuelinjection quantity is decreased to the fuel cut injection quantity orzero, the supply of the fuel to the engine 1 is stopped to complete theswitching of the driving sources to the motor-generator 5 and thetransition to the EV traveling. Here, during the switching of thedriving sources, specifically, during the torque of the engine 1 isdecreased, in the case where the accelerator pedal is pressed due to,for example, a change-of-mind of the driver, and the accelerator pedalopening APO is increased to be equal to or more than the predetermineddegree of opening APO1 again (time t3), it is necessary to return thedriving source to the engine 1 in order to allow the drive shaft torqueTSd corresponding to the accelerator pedal opening APO after theincrease to be achieved. In the comparative example, while the torqueincrease instruction is output to the engine 1, the supply of theelectric power to the motor-generator 5 is stopped to sharply decreasethe torque of the motor-generator 5. Since the torque increaseinstruction to the engine 1 until the engine torque actually starts tobe increased (time t4), there is a delay corresponding to the operationproperty of the engine 1. Therefore, in the drive shaft torque TSd,there is generated a shortage for an amount corresponding to the delayof the engine torque. In FIG. 6, the shortage amount of the drive shafttorque TSd caused by the delay of the engine torque is indicated by thediagonal line.

Now, the operation by the control according to the embodiment will bedescribed. In FIG. 5, the operation from time t1 where the acceleratorpedal is returned to transition the operating state to the first regionR1 on the low load side to time t3 where the accelerator pedal ispressed by, for example, a change-of-mind of the driver during theswitching of the driving sources to increase the accelerator pedalopening APO to equal to or more than the predetermined degree of openingAPO1 again is similar to that of the comparative example.

In the case of the embodiment, while the torque increase instruction isoutput to the engine 1 in response to the increase of the acceleratorpedal opening APO, a torque TM of the motor-generator 5 is increasedmore than that when the accelerator pedal opening APO is increased (timet3), and afterwards, the torque TM of the motor-generator 5 is decreasedwhen the change of an actual engine torque TE is shifted to the increase(time t4). Specifically, in order to allow the drive shaft torque TSdcorresponding to the accelerator pedal opening APO after the increase tobe achieved, the torque corresponding to the actual shortage amount ofthe engine torque with respect to the target value of the drive shafttorque TSd is generated by the motor-generator 5. This compensates theshortage amount of the drive shaft torque TSd caused by the delay afterthe torque increase instruction until the engine torque TE actuallystarts to be increased with the torque TM of the motor-generator 5, andensures securing the driving response of the vehicle in response to theincrease of the accelerator pedal opening APO. FIG. 5 illustrates astate where the inclination in the change of the torque TM of themotor-generator 5 is increased more than that before the increase of theaccelerator pedal opening APO in response to the increase of theaccelerator pedal opening APO, and furthermore, the change of the torqueTM of the motor-generator 5 is also shifted to the decrease from theincrease at time t4 where the change of the actual engine torque TE isshifted to the increase from the decrease. At time t5 where the torqueTM of the motor-generator 5 is decreased to zero, the torque TE of theengine 1 and the drive shaft torque TSd match to complete the switchingof the driving sources to the engine 1. Afterwards, the traveling isperformed with the engine 1 as the driving source.

FIG. 7 illustrates a case where the accelerator pedal is returned to astate of accelerator off (APO=0) from the state where the operatingstate is in the medium load region (APO≥APO1) (time t11), and the supplyof the fuel to the engine 1 is stopped. In this case, the switching ofthe driving sources is not performed, and the engine 1 continuouslyserves as the driving source. However, in this embodiment, maintainingthe clutch 3 in the engaged state and operating the motor-generator 5 asthe electric generator increase the load applied to the drive shaft 7from the engine 1 and the motor-generator 5. When the accelerator pedalis pressed and the accelerator pedal opening APO is increased (timet31), the regeneration operation of the motor-generator 5 is stopped andthe supply of the fuel to the engine 1 is resumed.

(Description of Operational Advantage)

The control device for the vehicle according to the embodiment isconfigured as described above. The following describes the effectsobtained by the embodiment.

First, during the switching of the driving sources, in the embodiment,when the accelerator pedal opening APO is increased to equal to or morethan the predetermined degree of opening APO1 during the switching ofthe driving sources from the engine 1 to the motor-generator 5, in otherwords, when the switching line (=APO1) is crossed over toward the secondregion R2 on the high load side due to the increase of the acceleratorpedal opening APO after the operating state is transitioned to the firstregion R1 on the low load side in the operating range map illustrated inFIG. 4, increasing the torque TM of the motor-generator 5 compensatesthe delay of the engine torque TE after the torque increase instructionuntil the torque TE of the engine 1 actually starts to be increased toensure suppressed generation of the shortage in the drive shaft torqueTSd. After the change of the engine torque TE is shifted to theincrease, decreasing the torque TM of the motor-generator 5 whileincreasing the torque TE of the engine ensures achieving the targetdrive shaft torque TSd while suppressing the generation of the shockcaused by the rapid decrease of the torque TM of the motor-generator 5.Thus, with the embodiment, when the accelerator pedal is pressed due to,for example, a change-of-mind of the driver during the switching of thedriving sources, the driving sources are appropriately controlled toensure securing the driving response of the vehicle while suppressingthe generation of the shock.

Second, setting the accelerator pedal opening (predetermined degree ofopening APO1) that determines the switching line of the driving sourcesto a different value depending on the vehicle speed VSP ensuresutilizing the operation properties of both the engine 1 and themotor-generator 5 to contribute to establish the efficient vehicle drivesystem P.

Third, when the accelerator pedal is completely returned from the statewhere the operating state is in the second region R2 to be in the stateof accelerator off (APO=0), continuously using the engine 1 as thedriving source and maintaining the clutch 3 in the engaged state ensureutilizing the engine brake and ensure securing the response atreacceleration. Furthermore, causing the motor-generator 5 to operate asthe electric generator, and recharging the electric power generated bythe electric generation to the battery 9 ensure improved efficiency ofthe whole vehicle drive system P.

The concepts extracted from the above description other than thosedescribed in claims are brought together below.

First, it is a control device for a vehicle. The vehicle includes adrive shaft, an engine coupled to the drive shaft, and an electric motorcoupled to the drive shaft. The control device for the vehicle includesa control unit that, when an accelerator pedal opening is increased tobe equal to or more than a predetermined degree of opening duringswitching of driving sources which decreases a torque of the enginegradually and increases a torque of the electric motor corresponding toa decrease of the engine torque, gives an instruction to increase atorque to the engine, and increases a changing rate of a torque of theelectric motor more than the changing rate of the torque of the electricmotor before the accelerator pedal opening is increased to equal to ormore than the predetermined degree of opening.

Second, it is the control device for the vehicle in which, after theaccelerator pedal opening is increased to equal to or more than thepredetermined degree of opening, the control unit sets a target torqueof the engine corresponding to the accelerator pedal opening after theincrease, and decreases the torque of the electric motor whileincreasing the torque of the engine toward the target torque.

Third, it is the control device for the vehicle in which thepredetermined degree of opening has a different value depending on avehicle speed.

Fourth, it is the control device for the vehicle in which the controlunit has a second region where the accelerator pedal opening is equal toor more than the predetermined degree of opening as an operating rangewhere a traveling is performed by the engine, and a first region wherethe accelerator pedal opening is less than the predetermined degree ofopening (excluding accelerator off state) as an operating range where atraveling is performed by the electric motor. The control unit executesthe switching of the driving sources when the operating state istransitioned from the second region to the first region.

Fifth, it is the control device for the vehicle in which the controlunit increases a load applied to the drive shaft from the engine and theelectric motor when an accelerator-on state is changed to anaccelerator-off state.

While the embodiment of the present invention has been described above,the present invention is not limited to this, and it is needless tomention that various changes and modifications can be made within arange of the matter disclosed in the claims.

The present application claims a priority of Japanese Patent ApplicationNo. 2017-165381 filed with the Japan Patent Office on Aug. 30, 2017, allthe contents of which are hereby incorporated by reference.

1.-4. (canceled)
 5. A control device for a vehicle, comprising: a driveshaft; an engine coupled to the drive shaft; an electric motor coupledto the drive shaft; and a controller configured to increase a torque ofthe electric motor more than the torque of the electric motor before anaccelerator pedal opening increases to equal to or more than apredetermined degree of opening when the accelerator pedal openingincreases to equal to or more than the predetermined degree of openingduring switching of driving sources in which the torque of the electricmotor is increased while a torque of the engine is decreased, anddecrease the torque of the electric motor while increasing the torque ofthe engine after a change of the torque of the engine turns to increasein association with the accelerator pedal opening increasing to equal toor more than the predetermined degree of opening.
 6. The control devicefor the vehicle according to claim 5, wherein the predetermined degreeof opening has a different value depending on a vehicle speed.
 7. Thecontrol device for the vehicle according to claim 5, wherein when anaccelerator-on state is changed to an accelerator-off state, thecontroller increases a load applied to the drive shaft from the engineand the electric motor.
 8. A control method for a vehicle, the vehicleincluding a drive shaft, an engine coupled to the drive shaft, and anelectric motor coupled to the drive shaft, the control methodcomprising: increasing a torque of the electric motor more than thetorque of the electric motor before an accelerator pedal openingincreases to equal to or more than a predetermined degree of openingwhen the accelerator pedal opening increases to equal to or more thanthe predetermined degree of opening during switching of driving sourcesin which the torque of the electric motor is increased while a torque ofthe engine is decreased, and decreasing the torque of the electric motorwhile increasing the torque of the engine after a change of the torqueof the engine turns to increase in association with the acceleratorpedal opening increasing to equal to or more than the predetermineddegree of opening.
 9. A control device for a vehicle, comprising: adrive shaft; an engine coupled to the drive shaft; an electric motorcoupled to the drive shaft; means for increasing a torque of theelectric motor more than the torque of the electric motor before anaccelerator pedal opening increases to equal to or more than apredetermined degree of opening when the accelerator pedal openingincreases to equal to or more than the predetermined degree of openingduring switching of driving sources in which the torque of the electricmotor is increased while a torque of the engine is decreased; and meansfor decreasing the torque of the electric motor while increasing thetorque of the engine after a change of the torque of the engine turns toincrease in association with the accelerator pedal opening increasing toequal to or more than the predetermined degree of opening.